The purpose of this project is to determine the effect of strengthening exercises on lymphocyte subpopulations (CD4 T cells, CD 8 T cells, Natural Killer Cells) in healthy adults. It is widely believed that regularly performed exercise helps improve resistance to infection. As a replicable and quantifiable stressor, the effect of exercise on immune function has interested numerous investigators. To our knowledge, this is the first study to look at the effects of strengthening exercises on changes in immune cell populations. Eight healthy, sedentary female subjects, ages 28-54, have completed the study. Four subjects exercised and 4 were control for each of two trials with different intensity and frequency of training. Peak torque and total work, and the percent and absolute numbers of CD4 T cells, CD8 T cells and NK cells were measured pre, during and post exercise. Upon comparing the direction and magnitude of changes in percent and absolute numbers of cells, there was no significant difference between the exercise groups and control groups in either trial 1 or trial 2. The intensity of exercise will be increased for the next group of subjects because no significant training effect was obtained. The next two groups will be men as per our protocol.